Small grindstones and hammer stones such as these were found alongside grindstones as wide as 2 feet (60 centimeters) at the Kush archaeological sites. Dated to between 2,000 and 1,500 B.C., the stones were used to grind ore, the team said. The ore then would have been washed with water to tease out gold flakes.

Kush's prowess in gold extraction came at a price.

Hunger for Kushite gold was one of the driving factors in the subjugation of the kingdom by Egypt's New Kingdom pharaohs. At one time, hundreds and even thousands of pounds of Kushite gold were sent to Egypt each year as tribute.